In WCDMA (wideband code division multiple access) and HSPA (high speed packet access), the radio network (RN) system is responsible for configuring the RLC (radio link control) window sizes in the UE (user equipment) so that the memory capability of the UE is not exceeded. The RLC protocol (Layer 2) operates in one of three modes: transparent; unacknowledged; and acknowledged mode (AM). The RLC protocol performs segmentation/re-assembly functions and, in acknowledged mode, provides an assured mode delivery service by use of retransmission. The RLC protocol provides a service both for control signaling (the Signaling Radio Bearer or SRB for short) and for user data transfer (the Radio Bearer or RB for short).
At call setup, the buffer capacity of the UE is signalled to the RN and the RN uses the UE buffer capacity to determine what size RLC windows to set up in the acknowledged mode. Some conventional techniques distribute the UE memory capacity for each radio bearer equally and do not account for or otherwise consider the actual transmission activity associated with each configured RB.
A radio bearer (RB) is a logical connection with a UE over the radio air interface and corresponds to a single data stream. A procedure for establishing an RB is described in Technical Specification 3GPP TS 25.931 v 5.1.0. For example, a UMTS Terrestrial Radio Access Network (UTRAN) responds to radio access service requests by allocating resources needed to support a communication with a UE. One RB may support a speech connection, another bearer may support a video connection, and a third bearer may support a data packet connection. Each RB is associated with quality of service (QoS) parameters describing how the RN should handle the data stream.
As the number of RBs using RLC acknowledged mode in the UE increases, a conventional RN correspondingly decreases the window size for each supported RB. This results in a peak throughput which is significantly lower than possible since the RLC window is of primary importance to facilitate high user data bit rates. Another drawback with the conventional system of handling RLC window sizes as described above is that there is a need to store unique RLC window values for each RB leading to extensive tables if the system supports multiple RB combinations. Every newly added RB must be assigned a unique RLC window size which in turn must be added to the table. As the number of RB combinations that are supported by the RN increases over time, so to does the cost of updating and maintaining the RLC window size tables. A table based solution with fixed values as outlined above also adversely affects the peak throughput in that the RLC window sizes are typically set to low values in order to address the worst case scenario in which all windows are full leading to overly conservative RLC window settings and a loss of peak throughput.